Western Daily Press (UK)
Children with autism have too many "junction boxes" in their brains, a study has found. The surplus synapses - places where neurons connect and communicate - are due to a lack of "pruning" that normally occurs early in life.
In mice with autistic traits, scientists were able to restore synaptic pruning and reduce symptoms with a drug used to suppress the immune systems of transplant patients.
The drug, rapamycin, has side effects that make it unsuitable as an autism treatment. But the discovery opens up exciting possibilities for other therapies based on synaptic pruning. Excessive synapses could be a fundamental causal factor behind autism, the scientists believe.
"This is an important finding that could lead to a novel and much- needed therapeutic strategy for autism," said Professor
Autism, which affects around 700,000 people in the
It is believed to be triggered by a combination of genetic and environmental factors that impact on the developing brain. During normal brain development, a burst of synapse formation occurs in infancy, especially in the cortex - a region closely linked to autistic behaviour.
Pruning removes more than half of these cortical synapses by late adolescence.
Synapses are known to be affected by many genes linked to autism, leading to speculation about the role they play in the condition.
Brains from 22 non-autistic children were used as a comparison.
Synaptic density in samples of brain tissue was measured by counting the numbers of tiny branching spines that make up neural connections.
By late childhood, spine density had dropped by about half in the "healthy" brains, but by only 16 per cent in the brains of autistic individuals.
"It's the first time that anyone has looked for, and seen, a lack of pruning during development of children with autism, although lower numbers of synapses in some brain areas have been detected in brains from older patients and in mice with autistic-like behaviours," said lead researcher Professor
Large amounts of the overactive protein were also present in the brains of autism sufferers, the scientists reported in the journal Neuron.
'Autism may still be treatable after a child is diagnosed'
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